Latching switch

ABSTRACT

A latching switch comprising two normally electrically isolated elements which mechanically latch when deflected in a prearranged sequence in substantially orthogonal directions. A contact edge on each element engages a contact pad on the other when the elements are latched, providing two conductor paths per pair of elements. Each element may comprise a bimetal, deflection thereof being effected via application of an actuating signal to one face of the bimetal, which face functions as a heating resistor.

United States Patent [191 Randall et al.

[111 3,743,977 [451 July 3,1973

[ LATCl-IING SWITCH [75] Inventors: Robert Scott Randall, Hazlet; RalphArnold Tengelsen, Parlin, both of NJ.

[73] Assignee: Bell Telephone Laboratories,

Incorporated, Murray Hill, NJ.

22 Filed: Apr. 27, 1972 21 Appl. No.: 248,044

[52] US. Cl. 337/77, 337/102, 337/359 [51] Int. Cl. H01h 61/02 [58]Field of Search 337/55, 75, 76, 77,

[56] References Cited UNITED STATES PATENTS 1,010,414 11/1911 Cubitt337/359 X 3,601,736 8/1971 Sepe 337/102 X 3,674,952 7/1972 Ellenberger337/77 X 3,370,142 2/1968 Burch et a1. 337/55 3,486,152 12/1969 Alban337/78 X 3,573,696 4/1971 Shaw 337/359 X 3,223,807 11/1965 Grahl 337/359X 1,640,257 8/1927 Stranszky 337/359 Primary Examiner-Bernard A.Gilheany Assistant Examiner-A. T. Grimley Attorney-W. L. Keefauver eta1.

[57] ABSTRACT A latching switch comprising two normally electricallyisolated elements which mechanically latch when deflected in aprearranged sequence in substantially orthogonal directions. A contactedge on each element engages a contact pad on the other when theelements are latched, providing two conductor paths per pair ofelements. Each element may comprise a bimetal, deflection thereof beingeffected via application of an actuating signal to one face of thebimetal, which face functions as a heating resistor.

11 Claims, 6 Drawing Figures Patented July 3, 1973 3 Sheets-Shoot lPatented July 3, 1973 3,143,971

3 Sheets-Shut 2 SWITCH l0 3 Sheets-Shut 3 FIG. 5

DE FLECTION 2|] SWITCH IO (TOP VIEW) FIG. 6

-:T|P" I I RELEASE l30\ r I I H 1 L m DEFLECJTLQN w (FRONT VIEW)LATCHING SWITCH BACKGROUND OF THE INVENTION This invention relates tolatching switches and, more particularly, to latching switches adaptedfor use in crosspoint matrices.

In certain crosspoint matrix applications the time necessary to operate,i.e., to open or close, a selected crosspoint is negligible compared tothe time the crosspoint is to remain closed. Accordingly, economicaloperation of the matrix requires that no energy be expended inmaintaining crosspoint closure. To this end, arrangements have beendevised in which each crosspoint comprises a latching switch. Thecontact elements at a crosspoint latch mechanically when deflected andreleased in a prearranged sequence. The mechanical latching of thecontact elements thereby obviates expenditure of energy to maintainswitch closure.

In such known arrangements, deflection and release of the crosspointcontact elements is generally effected via electromechanical actuatingapparatus such as relays, solenoids, and push rods. Although generallysatisfactory, the actuating apparatus tends to be bulky and expensive ascompared to the crosspoint elements themselves.

In some crosspoint matrices, such as those employed in telephoneswitching offices, multiple conductor paths are to be established when acrosspoint is closed. In known arrangements this is effected byutilizing multiple tandemly-operated contact element pairs at eachcrosspoint.

SUMMARY OF THE INVENTION Accordingly, a general object of the inventionis to provide an improved latching switch.

A more specific object of the invention is to provide an improvedlatching switch adapted for use in crosspoint matrices.

A further object of the invention is to provide an improved latchingswitch having simple, compact and economical actuating apparatus.

Yet another object of the invention is to provide an improved latchingswitch which provides more than one signal path per pair of contactelements.

These and other objects are achieved in a latching switch comprisingfirst and second contact elements each of which has a fixed end and afree end. The free end terminates in a contact finger which carries acontact edge lying on a line extending between the fixed and free end.The free end of each element further includes a contact pad electricallyisolated from the contact edge and disposed between the fixed end andthe contact edge.

The first and second contact elements are adapted for deflection insubstantially orthogonal directions such that the contact pad andcontact edge of each element substantially concurrently intersect therelease paths of the contact edge and contact pad, respectively, of theother element. The switch is closed via deflection and subsequentsubstantially concurrent release of the contact elements, electricalcontact being established between the contact edge of one element andthe contact pad of the other. Thus, the present invention advantageouslyprovides two independent signal paths per pair of contact elements.

If desired, deflection and release of the contact elements may beeffected by known electromechanical apparatus. However, each element mayadvantageously comprise a bimetal, one face of the element including alayer of relatively high thermal expansion coefficient metal and theother a layer of relatively low thermal expansion coefficient material.Deflection of each ele ment is then effected electrothermally.

In accordance with one aspect of the invention, the metal layer on oneface of each element illustratively comprises a heating resistor,thereby obviating the need for a separate electrothermal actuatingdevice. The metal layer on the other face comprises first and secondelectrically isolated signal conductors which respectively connect thecontact pad and contact edge of the element to a pair of switchterminals at the fixed end of the element.

In accordance with another aspect of the invention,

the two faces of each element are separated by an insulating layer whichisolates the first and second signal conductors from the heatingresistor and also from each other.

BRIEF DESCRIPTION OF THE DRAWING These and other objects and features ofthe invention may be clearly understood from the following detaileddescription in which: 7

FIGS. 1-4 are perspective views of various stages of operation of anillustrative embodiment of a latching switch according to the invention;and

FIGS. 5 and 6 are detail top and side views, respectively, of the switchin a latched configuration as shown in FIG. 4.

DETAILED DESCRIPTION Latching switch 10 shown in FIGS. 1-4 is comprisedof resilient contact elements and 200. Element 100 has a release face106 and a deflection face 105, only the upper edge of the latter beingvisible in FIGS. 1-4. Element 100 extends axially between a free end-114and a fixed end 109 which is secured to a rigid support 101. Free end114 terminates in finger 110 and edge 120. Finger 110 includes a contactedge 111 which lies on a line extending between fixed end 109 and freeend 114. Contact edge 111 is electrically connected to switch terminalvia signal conductor 113 which runs along release face 106.

Free end 114 further includes on release face 106 a contact pad 121which is bounded by edge and is disposed between fixed end 109 andcontact edge 111. Contact pad 121 is electrically connected to switchterminal 125 via signal conductor 123. The latter runs along releaseface 106 and is electrically isolated from signal conductor 113 byinsulating strip 118.

Illustratively, element 200 is substantially identical to element 100.Accordingly, a corresponding numbering scheme is employed in thedrawing, element 200 having deflection and release faces 205 and 206,fixed and free ends 209 and 214, and so forth.

When switch 10 is open, elements 100 and 200 assume the undeflectedpositions shown in FIG. 1, element 100 being somewhat below and forwardof element 200. The switch is closed by sequentially bending elements100 and 200 toward their respective deflection faces, i.e., deflectingthem, and then allowing them to unbend, i.e., to release substantiallyconcurrently. As more fully described hereinafter, this causes elements100 and 200 to latch with each other and thereby close the switch.Deflection and release of elements 1110 and 200 may be effected, forexample, by known electromechanical apparatus such as relays, solenoidsand push rods. However, as described below, a preferred embodiment ofthe invention utilizes. the thermostatic action of bimetals for thispurpose.

When it is desired to close switch 10, element 100 is deflected in thedirection indicated in FIG. 1. Element 1011 thus passes under element200 and, when fully deflected, is positioned behind corner edge 231 ofelement 200 as shown in FIG. 2. Element 200 is then deflected in thedirection indicated in FIG. 2, which direction is substantiallyorthogonal to the direction in which element 100 is deflected. Whenfully deflected, elements 100 and 200 assume the positions shown in FIG.3. It will be appreciated that the deflected configuration of FIG. 3 canalso be achieved by deflecting elements 100 and 200 in the oppositesequence to that just described.

Finally, elements 100 and 200 are released substantially concurrently.However, before element 200 can fully release to its undeflectedposition, finger 110 enters the release path of contact pad 221. At thesame time, element 100 is prevented from fully releasing to itsundeflected position, because finger 210 enters the release path ofcontact pad 121. Accordingly, elements 100 and 200 engage each other andlatch as shown in FIG. 4. Contact edge 111 of finger 110 contacts pad221 of element 200 so that a first signal path is established betweenswitch terminals 115 and 225 via signal conductors 113 and 223. Inaddition, contact edge 21 1 of finger 210 contacts pad 121 so that asecond signal path is established between terminals 124 and 215 viasignal cnductorsl23 and 213. Thus, when closed, the present latchingswitch, while utilizing but a single pair of contact elements,advantageously provides two independent signal paths.

Switch 10 can be reopened in several ways. For example, if element 100is deflected behind corner edge 231, element 200 will return to itsundeflected position (see FIG. 2). Element 100 can then be released toits undeflected position (FIG. 1). Alternatively, both switches can bedeflected concurrently and then released in sequence. Other ways ofreopening switch 10 will be readily apparent.

FIGS. 5 and 6 are detail top and front views, respectively, of switch 10when elements 100 and 2011 are in the latched configuration of FIG. 4.In FIG. 5, element 100 deflects and releases as indicated, and element200 deflects into and releases out of the plane of the drawing. FromFIG. 5 it is apparent that element 1110 is adapted for deflection andrelease such that contact pad 121 intersects the release path of edge211 at the same time that finger 1111, and hence contact edge 111,intersect the release path of contact pad 221.

In the front view of switch 10, shown in FIG. 6, element 200 deflectsand releases as indicated, while element 100 deflects into and releasesout of the plane of the drawing. From FIG. 6 it is apparent that element200 is adapted for deflection and release such that contact pad 221intersects the release path of edge 111 at the same time that finger210, and hence contact edge 211 intersect the release path of pad 121.

Thus,- it is seen that an important criterion which must be satisfied toensure latching of elements 100 and 200 is that each element must beadapted for deflection such that its contact pad and contact edgesubstantially concurrently intersect the release paths of the constantedge and contact pad, respectively, of the other element.

As mentoioned above, elements and 200 may be deflected and released byknown electromechanical apparatus. Alternatively, the thermostaticaction of bimetals can advantageously be used for this purpose. One faceof each'switch element may include a layer of relatively low thermalexpansion coefficient metal, while the other face includes a layer ofrelatively high thermal expansion coefficient metal. Deflection andrelease of each element is then effected by regulating its temperature.Illustratively, a heating coil adjacent the fixed end of the element maybe employed for this purpose. Utilization of bimetals as the contactelements of a latching switch is disclosed, for example, in patentapplication (M. A. Townsend 20), filed of even date herewith andassigned to the assignee hereof.

In accordance with a feature of the present invention, the need for aseparate heating device to deflect the bimetallic contact elements isobviated by utilizing the metal layer on one face of each element as aheating resistor. As shown in FIGS. 4-6, contact element 100, forexample, includes resistor path on its deflection face 105.Illustratively, resistor path 130 comprises a layer of a metal having athermal expansion coefficient which is small relative to that of signalconductors 113 and 123. Element 100 is actuated by a signal applied toterminal points 131 and 132 of resistor path 130. As the temperature ofelement 100 is thus increased, conductor paths 113 and 123, whichcomprise a layer of relatively high thermal expansion metal, expand to agreater extent than does resistor path 1311. Accordingly, element 101)deflects toward its deflection face 1115. Release of element 100 iseffected by terminating the actuating signal at terminals 131 and 132,thereby allowing element 100 to return to ambient temperature.

Element 100 additionally includes insulating layer 133 which insulatesresistor path 130 from signal conductors 113 and 123. Insulating layer133 (which may include insulating strip 118) isolates the actuatingsignals through resistor path 130 from the signals on conductors 113 and123.

It will be appreciated, as shown in FIGS. 4-6, that element 2110 maysimilarly comprise a bimetal including a resistor path as describedhereinabove for element 100. The following materials have been found tobe well adapted for use in a bimetallic contact element such as element100: for signal paths 113 and 123, beryllium-copper; for resistor path130, the nickeliron-cobalt alloy sold under the trademark KOVAR; and forinsulating layer 133, epoxy impregnated glass cloth. Of course, othersuitable materials will be apparent to those skilled in the art.

As may be seen in FIG. 4, elements 100 and 200 are somewhat deflectedwhen switch 10 is closed. Thus, a moderate rise in ambient temperature,while somewhat decreasing the contact pressure between elements 100 and200, advantageously will not disrupt closure of the signal paths betweenthe terminals of switch 10.

It is to be understood that the foregoing merely illustrates theprinciples of the invention and that further modifications andembodiments-of the invention may be devised by those skilled in the artwithout departing from the spirit and scope thereof.

We claim:

1. A latching switch comprising; first and second contact elements eachhaving a fixed end and a free end, said free end having a contact edgelying on a line extending between said fixed end and said free end andfurther having a contact pad disposed between said fixed end and saidcontact edge, each of said contact elements further including means forelectrically isolating said contact pad from said contact edge; andmeans adapting said elements for individual deflection in substantiallyorthogonal directions such that the contact pad and contact edge of eachof said elements substantially concurrently intersect the release pathsof the contact edge and contact pad, respectively, of the other of saidelements; whereby electrical contact is established between the contactedge of each of said elements and the contact pad of the other of saidelements upon deflection and subsequent substantially concurrent releaseof said elements.

2. A latching switch in accordance with claim 1 wherein each of saidelements comprises a bimetal, and wherein said adapting means includesmeans for individually regulating the temperature of each of saidelements.

3. A latching switch comprising; first and second contact elements, eachof said contact elements comprising a bimetal having first and secondelectrically isolated layers, one of said first and second layersincluding means for individually regulating the temperature of each ofsaid elements, each of said contact elements further having a fixed endand a free end, said free end having a contact edge lying on a lineextending between said fixed end and said free end and further having acontact pad electrically isolated from said contact edge and disposedbetween said fixed end and said contact edge; means including saidregulating means adapting said elements for individual deflection insubstantially orthogonal directions such that the contact pad andcontact edge of each of said elements substantially concurrentlyintersect the release paths of the contact edge and contact pad,respectively, of the other of said elements.

4. A latching switch in accordance with claim 3 wherein said regulatingmeans comprises a resistive path for heating said bimetal in response toa signal applied to said path.

5. A latching switch in accordance with claim 4 wherein the other ofsaid first and second layers of each element comprises first and secondelectrically isolated conductors extending from the contact edge andcontact face, respectively, of said element to the fixed end thereof.

6. A latching switch comprising, first and second contact elementsindividually operative for deflection and release in substantiallyorthogonal directions, first and second contact pads respectivelydisposed on said first and second elements, first and second contactfingers respectively disposed on said first and second elements, meansdisposed on said first element for electrically isolating said firstcontact fingerfrom said first contact pad, and means disposed on saidsecond element for electrically isolating said second contact fingerfrom said second contact pad, said first and second fingers beingindividually operative upon release of said first and second contactelements, respectively, for contacting said second and first contactpads, respectively.

7. A latching switch in accordance with claim 6 further comprising anindividual pair of switch terminals associated with each of saidelements, and first and second conductors disposed on each said elementrespectively connecting the contact pad and contact finger on saidelement to said pair of terminals associated therewith.

8. A latching switch in accordance with claim 6 wherein each of saidelements comprises a bimetal, said switch further including means forindividually regulating the temperature of each of said elements.

9. A latching switch comprising; first and second contact elementsindividually operative for deflection and release in substantiallyorthogonal directions, each of said elements comprising a bimetal havingfirst and second metal layers and a layer of insulating materialseparating said first and second layers, one of said first and secondlayers including means for individually regulating the temperature ofeach of said elements; first and second contact pads respectivelydisposed on said first and second elements; first and second contactfingers respectively disposed on said first and second elements andelectrically isolated from said first and second contact pads, saidfirst and second fingers being individually operative upon release ofsaid first and second contact elements, respectively, for contactingsaid second and first contact pads, respectively; an individual pair ofswitch terminals associated with each of said elements; and first andsecond conductors disposed on each said element respectively connectingthe contact pad and contact finger on said element to said pair ofterminals associated therewith.

10. A latching switch in accordance with claim 9 wherein said regulatingmeans comprises a resistive path for heating said bimetal in response toa signal applied to said path.

11. A latching switch in accordance with claim 10 further comprising anindividual pair of switch terminals associated with each of saidelements and wherein the other of said first and second layers of eachsaid element comprises first and second electrically isolated conductorsextending from the contact edge and contact face, respectively, of eachsaid element to said pair of terminals associated therewith.

1. A latching switch comprising; first and second contact elements eachhaving a fixed end and a free end, said free end having a contact edgelying on a line extending between said fixed end and said free end andfurther having a contact pad disposed between said fixed end and saidcontact edge, each of said contact elements further including means forelectrically isolating said contact pad from said contact edge; andmeans adapting said elements for individual deflection in substantiallyorthogonal directions such that the contact pad and contact edge of eachof said elements substantially concurrently intersect the release pathsof the contact edge and contact pad, respectively, of the other of saidelements; whereby electrical contact is established between the contactedge of each of said elements and the contact pad of the other of saidelements upon deflection and subsequent substantially concurrent releaseof said elements.
 2. A latching switch in accordance with claim 1wherein each of said elements comprises a bimetal, and wherein saidadapting means includes means for individually regulating thetemperature of each of said elements.
 3. A latching switch comprising;first and second contact elements, each of said contact elementscomprising a bimetal having first and second electrically isolatedlayers, one of said first and second layers including means forinDividually regulating the temperature of each of said elements, eachof said contact elements further having a fixed end and a free end, saidfree end having a contact edge lying on a line extending between saidfixed end and said free end and further having a contact padelectrically isolated from said contact edge and disposed between saidfixed end and said contact edge; means including said regulating meansadapting said elements for individual deflection in substantiallyorthogonal directions such that the contact pad and contact edge of eachof said elements substantially concurrently intersect the release pathsof the contact edge and contact pad, respectively, of the other of saidelements.
 4. A latching switch in accordance with claim 3 wherein saidregulating means comprises a resistive path for heating said bimetal inresponse to a signal applied to said path.
 5. A latching switch inaccordance with claim 4 wherein the other of said first and secondlayers of each element comprises first and second electrically isolatedconductors extending from the contact edge and contact face,respectively, of said element to the fixed end thereof.
 6. A latchingswitch comprising, first and second contact elements individuallyoperative for deflection and release in substantially orthogonaldirections, first and second contact pads respectively disposed on saidfirst and second elements, first and second contact fingers respectivelydisposed on said first and second elements, means disposed on said firstelement for electrically isolating said first contact finger from saidfirst contact pad, and means disposed on said second element forelectrically isolating said second contact finger from said secondcontact pad, said first and second fingers being individually operativeupon release of said first and second contact elements, respectively,for contacting said second and first contact pads, respectively.
 7. Alatching switch in accordance with claim 6 further comprising anindividual pair of switch terminals associated with each of saidelements, and first and second conductors disposed on each said elementrespectively connecting the contact pad and contact finger on saidelement to said pair of terminals associated therewith.
 8. A latchingswitch in accordance with claim 6 wherein each of said elementscomprises a bimetal, said switch further including means forindividually regulating the temperature of each of said elements.
 9. Alatching switch comprising; first and second contact elementsindividually operative for deflection and release in substantiallyorthogonal directions, each of said elements comprising a bimetal havingfirst and second metal layers and a layer of insulating materialseparating said first and second layers, one of said first and secondlayers including means for individually regulating the temperature ofeach of said elements; first and second contact pads respectivelydisposed on said first and second elements; first and second contactfingers respectively disposed on said first and second elements andelectrically isolated from said first and second contact pads, saidfirst and second fingers being individually operative upon release ofsaid first and second contact elements, respectively, for contactingsaid second and first contact pads, respectively; an individual pair ofswitch terminals associated with each of said elements; and first andsecond conductors disposed on each said element respectively connectingthe contact pad and contact finger on said element to said pair ofterminals associated therewith.
 10. A latching switch in accordance withclaim 9 wherein said regulating means comprises a resistive path forheating said bimetal in response to a signal applied to said path.
 11. Alatching switch in accordance with claim 10 further comprising anindividual pair of switch terminals associated with each of saidelements and wherein the other of said first and second layers of eachsaid element comprises first and Second electrically isolated conductorsextending from the contact edge and contact face, respectively, of eachsaid element to said pair of terminals associated therewith.